Quick comparison of LSNs and NAT64

Mark Andrews marka at isc.org
Thu Jun 9 03:31:43 CDT 2011


In message <4DF053AA.50400 at axu.tm>, Aleksi Suhonen writes:
> Hello,
> 
> Some people were talking about Large Scale NATs (LSN) or Carrier Grade 
> NATs (CGN) yesterday. Comments included that DS-Lite and NAT64 are 
> basically LSNs and they suffer from all the same problems. I don't think 
> that NAT64 is as bad as other LSNs and here's why:
> 
> NAT64 scales much better than NAT44 and NAT444(*)
> 
> The trick is with its companion DNS64. If you need more NAT64 capacity, 
> you can just add more NAT64 boxes with unique /96 prefixes around your 
> network and have your DNS64 load-balance traffic to those boxes. You can 
> also map one A record into two AAAA records of different NAT64 boxes, in 
> case that works better with some application protocols.

You can add more capacity with DS-Lite as well though it does take a while
for the DHCP option to be refreshed without push support.

> The smallest granularity of load-balancing easily available with NAT444 
> is per customer or per customer group. DNS64 allows per flow granularity 
> for load-balancing without even breaking a sweat.
> 
> I've been testing NAT64 at home using a public NAT64 trial and generally 
> I've been very happy with it:
> 
> http://www.trex.fi/2011/dns64.html
> 
> A neat feature I've liked is that I don't have to pass all my traffic 
> via the NAT64 box, and so it doesn't have to be between me and the 
> Internet. NAT44 usually acts as a fuse between me and my Internet.

You don't have to pass all the traffic through the AFTR box or the
LSN when dual stacked either.  The AFTR box can be on the other
side of the world or out sourced if you want it to be.  The same
can be done with NAT64.

> The biggest downsides I've encountered are:
> 
> I.   Some streaming websites use IP addresses in their video stream 
> URLs, so DNS64 doesn't get asked and that traffic won't flow via NAT64. 
> Thankfully these are a minority.

Not a problem with DS-Lite or NAT444.
 
> II.  Networked games usually use some sort of a tracker to help clients 
> find games to connect to, and those only use plain IP addresses too. And 
> some games only query for A records, and thus can't benefit from DNS64 
> either.

Not a problem with DS-Lite or NAT444
 
> So I guess the optimal way to stretch the lifetime of IPv4 while still 
> moving toward IPv6 all the time would be to dual-stack customers and 
> deploy both NAT64/DNS64 and some other LSN which can handle the two 
> downsides above. All the traffic that you can shift to NAT64 means that 
> your other LSN (which doesn't scale as well) can handle that much more 
> traffic before becoming a bottleneck. And naturally, you'll want to 
> shift all that youtube/facebook/whatever traffic to native IPv6 to help 
> both NAT boxes cope.
> 
> My 2 cents delivered,
> 
> -- 
>          Aleksi Suhonen
> 
> 	() ascii ribbon campaign
> 	/\ support plain text e-mail
> 
> (*) NAT44 means the normal NAT from private IPv4 addresses to public 
> IPv4 addresses. NAT444 means that there are two layers of NAT boxes: 
> usually one at customer premises and the other at the ISP, doing LSN.
> 
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org




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